SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ddc79d066e57217e7168597eff953406cdcf4070c359b85366c13b1e637c2bf6' 
  AND token = 'wel4JK5QEWlhZB6W9OqKN/qt8wYM+hd2soEh1vSOZgo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}